Method for the preparation of selenides and tellurides



United States PatentC 3,023,080 METHOD FQR TEE PREPARATIGN F SELENHDES AND TELLURIDES Stanley M. Kulitay, Dayton, Ohio, assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Filed Sept. 12, 1%58, Ser. No. 760,568

Claims. (Cl. 23-50) crotonic acids, as a precipitating agent and using simple apparatus. Various unsaturated organic acid reducing agents may be used including maleic, fumaric, and acrylic acids in the present invention.

of the group of organic acid reducing agents and crotonic acids. I

It is also an object of the invention to prepare metal binary, ternary and higher compounds-,such as tellurides, selenides, antimonides, and arscndies having a preare malonic ciselyssontrolled stoichiometric or non-stoichiometric composition. In general, the present method makes it possible to prepare various mixed compounds, that is, doped ternary and higher compounds,, as distinguished from straight binary compounds. It is also an object of the invention to prepareuniformly doped metal tellurides, selenides, antimonidesand arsenides by precipitating such modified compounds by means of crotonic and malonic acids and other organic acid salts, derivatives and analogues.

It is a further object of the invention to prepare in good yield various binaries, such as tellurides, selenides, antimonides, and arsenides and other compounds of metals selected from the group consisting of mercury, platinum, palladium, lead, tin, nickel, cobalt, cadmium, thallium, indium, antimony, bismuth, ruthenium, rhodium, osmium, iridium, copper, silver, gold, tellurium and selenium, by precipitation from soluble compounds by means of crotonic and malonic acids or thevarious reducing agents set forth above. The compounds which are made by the present method include such compounds as'silver mercuride.

The prior art methods which have been available for the preparation of semiconductor-type compounds have suiiered a disadvantage in that it has been difficult to achieve precise or predictable stoichiometric proportions which are necessary in order to obtain controlled semiconductive properties. For example, the conventional method of preparing mercury telluride has been a relatively high-temperature, long-time (up to 80 hours) fusion of the respective elements. Another method for the preparation of mercury telluride has been by the reaction of solutions of mercury salts with the highly toxic, exceedingly unstable hydrogen telluride in complicated apparatus. Both of these prior art methods have yielded non-stoichiometric mixtures which, being inherently unbalanced, were unpredictable for use as a semiconductor material.

Another difiiculty encountered in the methods of the prior art has been the quantitative control of doping additives. Such additive materials are employed in minorproportions, which have been 'diflicult to introduce in the The preferred members 3,023,030 Patented Feb. 27, 1962 1 precise amounts required to obtain the desired semiconductive properties.

The present method also eliminates the difiicult purifiaction of metal tellurides, selenides, antimonides and arsenides which involves distilling off the unreacted components at high temperatures from the crude compounds obtained by conventional methods. One of the difliculties which has attended distillation purification is the partial decomposition of the product, with a consequent loss of the desired stoichiometric proportion.

Another advantage of the present method is that it avoids the necessity of first isolating solids such as sole nites and tellurites for subsequent reductionthe selehide or telluride is produced directly from. solutions of the metals and/or metalloids.

In one embodiment of the present invention the process begins with the production of a solution of the desired purity containing the dissolved compounds of the specific metal or metals and of tellurium, selenium, antimony, or arsenic. The components may also be introduced as the respective elements or compounds which are dissolved or vaporized for further reaction. However, the invention may be carried out in any desired medium, preferably selected from the group consisting of solutions, melts and vapors. The media contemplated in the present invention embrace solutions of the metal ions, including tellurium, selenium, antimony and arsenic as well as liquid media, such as melts exemplified by molten chloride, such as selenium chloride and bismuth chloride. Vapor phase media are also included, for example, mercuric chloride and tellurium chloride with or without a carrier gas.

The concentration employed when solutions are used will be dictated in large part by the solubility of the respective compounds, for example, chlorides or nitrates of mercury, lead, tin, nickel, cobalt, cadmium, thallium, indium, arsenic, antimony, bismuth, platinum, palladium, ruthenium, rhodium, osmium, iridium, copper, silver, gold, tellurium, selenium and combinations thereof. In general, the concentration of the soluble metal salt and of the soluble tellurium, selenium, antimony, or arsenic compound may range up to the solubility limits of the respective compounds. For example, in preparing mercury selenide the mercuric nitrate was employed as a 20% solution, while the selenous acid was used in 10% to 15% by weight solution. The source materials of the said tellurides, selenides, antimonides and arsenides are preferably the acid solutions of the element or oxide or any pure, soluble compound. In general, the proportion of the organic acid reducing agent which is employed is 0.1 to 25.0 g. molecular weight (mole) of the said organic acid reducingagent per gram atomic weight of the said telurium, selenium, antimony, or arsenic. A preferred range is from 1.0 to 15 gram molecular weights. When the reducing agents are mentioned herein, such expressions include not only the reducing agents, per se, but also their commercial solutions and derivatives.

The solution as described above may be heated in order to increase the solubility of the respective compounds therein. The pressure under which the process is conducted is usually atmospheric, but is not critical, and moderate pressure may be employed. The time required for the reaction is also a non-critical factor, although reaction appears to be complete after the first few minutes.

The precipitation of the desired metal tellurides, selenides, arsenides and antimonides is preferably carried out by adding a combined solution or individual solutions of the said starting materials to a solution of mixed aqueous crotonic and malonic acids or other organic acid reducing agent. However, the three solutions of the anion, the cation and the reductant may also be mixed simultaneously, or by first adding thhe reductant to one of the reactants, or to the combined mixture. The strength of such solutions is not critical, although it is necessary to operate with an excess of the solution containing the reductant such as crotonic and malon ic acids. Themes ent invention may employ either a liquid medium for the precipitation as described above, or 'a spray typ'e" of precipitation employing liquid sprays of some ofthe starting materials, such as themetal salts' and /or the reducing agent The above discussion has been concerned chiefly with the preparation of stoichiometric compounds. However, non-stoichiometric compositions may readily be'm'ad'e by the present method by employing an excess ofeith'er the anion or the cation. For example, an excess of 1% by weight of silver introduced in the preparation'of silver selenide results in the production of a' uniform product having 1% silver as free metal in excess of the theoretical Ag Se. The working solutions describedabove may also contain therein any desired" soluble doping compound capable of reduction to the element by the reducing agent, such as copper, silver, gold or the platinum metals. v The by-products of the reaction are water-soluble and accordingly can be removed from the products by simple filtration and washing. The temperature employed in carrying out the invention may be from 20 C. to 150C. in'aqueous systems or 20 C. to 200 C. in vapor systemsin orde'r' to obtain a reduction to the desired metal sie lenide, tellt'iride, ans: monide, or arsenide. ii fi L Another embodiment of the present invention based upon the precipitation of binary, and mixed compounds; such as ternary and higher compounds by organic acid reducing agents is the employment of a complexing agent in the precipitation. Preferred complexing agents in present invention include the group of tartaric acid, citric acid and malic acid. It has been found that theuseof the said complexing agents makes it possible to carry the precipitation without'incurring the precipitation of metal hydroxides or other contaminating basic com pounds. The proportion of the complexing agents, such as tartaric acid, may be varied widely, such as over the range of from 0.1% to 20% by weight relative to the \"eight of the total solution present. i The following examples illustrate specific embodiments of the present invention.

Example 1 The preparation of mercury selenide was carried out by first weighing out 2.0436 g. of mercury which was dissoived with ml. of 1:1 nitric acid. The selenium was provided as 0.8040 g. of the powdered element, in equivalent stoichiometric proportion with the mercury. Tlie selenium was dissolved in a separate beaker with ,the'aid of 9 ml. of 2:1 nitric acid in water. I i

A solution containing the crotonic-malonic acid pr cipitating agent was prepared from gl'pf crotonic acid and 15 g. malonic acid dissolved in 300 ml. water. The acids were completely dissolved at room temperature after which the solution of selenium, then the mercury compounds was added thereto slowly with constantstirring, followed by 35 ml. concentrated ammonium hydroxide. Upon boiling, a precipitate of mercury selen'ide which formed soon became a dense, black powder. After boiling for90 minutes, the product wasobtained by tering the solution and washing the precipitate with water, followed by methanol. The product was dried lat. 95 C. It was analyzed by X-ray dilfraction analysis and was found to be face-centered cubic in structure and to have the stoichiometric proportion of the compound HgSe. The lattice constantfor the compound wasj6.077 A. No other crystalline material, such as uncombined Te, could be detected.

Example 2 The preparation of beta-silver selenide, Ag Se,

carried out by first preparing'separate solutions of 3.3978

g. ofsilver nitrate in 15 ml. water, and 0.7896 g. of powdered selenium in 9 ml. of 2:1 nitric acid. The seleniurn solution was added to a solution consisting of 15 g. each of malonic and crotonic acids and 300 ml. water at room temperature, followed by'the silver solution, then 18 ml. ammonium hydroxide. This was then boiled and handled in accordance with the method of'Example 1. The product'was' obtained in 97.0% yield as a dark gray microcrystalline powder whose D value for lattice constant by X-ray diffraction examinationagreedwiththose in the literature (ASTM) "for beta-silver selenide (naumannite).

were

The preparation of palladium selenide, PdSe was conducted by first dissolving 0.53'20'giofpalladium i'n'8 ml. 1:1 aqua r'egia'hi water and 0.7896 g. 'of'powdei'ed seleniuin'in 9 ml. 2:1 nitric acid in'wat'er. The combined solutions 'were then added to 'a boiling solution or 15 g; eachof crotonic and malonic acids and 300 ml. of water. No ammonium'hydroxide wasused. This was then handled in accordance with the method of Example 1. The product was'ob'tained in 92.5% y'ield'as a black powder which, where xamined' by 'X-ray' difiraction means, revealed it""t'o' be amorphous and therefore impossible to verifyby X;raymearis'.'Ihat itwa's indeed ease," and not'a simple mixture of Pd and Se was in dic'atedby' its 'non-ra'ctivity'with 1":1 nitric acid, which reacts instantly with selenium to prodpce' brovlVnNO- fumes.

What is claimed is l Method'for the preparation of a compound selected fr'om'the class consisting of mercury, platinum, palladium, lead, tin; nick'lfcobalt, cadmium, thallium, indium, bismuth, ruthenium,'rh'odium, osmium, iridium, copper, silver "and gold "tellur'ides "and selenides which comprises precipitating the desired compounds from media containing'the respective membersthereof by 'admixture with a precipitating ag'entconsistingofa member ofthe class "of croto'riic and malonica'cids in the proportion'of' from" 0.1 to' 2510' moleculafweight per atomic weight of tellurium and selenium, and isolating the desired compound fromthe mixture. i

2. Method for the preparation of a compound sele6ted"from the class consisting'pf mercuryf pl'atinunr, palladium, lead, tin, nickel, "cobalt, cadmium, thallium, indium, bismuth, "ruthenium, rhodium, osmium, iridium, copper, silver" and "gold selenidesand t'cllurides,"which comprises precipitating the desired compound from solutions'containing the respective ions thereof by admixture with a solution of crotonic acid, in the proportion'of from 0.1' to 25 .O'molecular weights per atomic weight of the said selenium andtellurium'and' isolating the desired compound from the mixture.

3. Method for the preparation of a compound selected from the class consisting of mercury, platinum, palladium, lead, tin, nickel, cobalt, cadmium; thallium, indium,'bismuth, ruthenium, rhodium, osmium, iridium, copper, sil- V621 and gold tellurides and selenides which comprises precfipitatingthe desired compound from solutions containingthe respective ions thereof .by admixture with a solution of crotonic and mal'onic acids in the proportion of from 0.1 to 25.0 molecular weights per atomic weight of the said selenium and telluriurn and isolating the desired compound from the mixture.

4. Method forthe preparation of a compound selected from theclass consisting of mercury, platinum, palladium, lead, tin, nickel, cobalt, cadmium, thallium, indium, bismuth, ruthenium, rhodium, osmium, iridium, copper, silver and gold tellurides and selenides which comprises precipitating the desired compound from solutions containingtherespective ions thereof by admixture with a Solution of malonic acid in the proportion of from OLi to mol cu a ei htsne a omic wei o t t d selenium and tellurium and isolating the desired compound from the mixture.

5. Method for the preparation of mercury selenide which comprises precipitating dissolved mercury and selenium ions by admixture with a mixture of aqueous crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular weight per atomic weight of selenium, and isolating the desired compound from the mixture.

6. Method for the preparation of palladium selenide Which comprises precipitating dissolved palladium and selenium ions by admixture with a mixture of aqueous crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular weight per atomic Weight of selenium, and isolating the desired compound from the mixture.

7. Method for the preparation of silver selenide, which comprises precipitating dissolved silver and selenium ions by admixture with a mixture of aqueous crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular Weight per atomic weight of selenium, and isolating the desired compound from the mixture.

8. Method for the preparation of bismuth telluride, which comprises precipitating dissolved bismuth and tellurium ions by admixture with a mixture of aqueous crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular weight per atomic Weight of tellurium, and isolating the desired compound from the mixture.

9. Method for the preparation of platinum telluride, which comprises precipitating dissolved platinum and tellurium ions by admixture with a mixture of aqueous crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular weight per atomic weight of tellurium, and isolating the desired compound from the mixture.

10. Method for the preparation of compounds selected from the class consisting of mercury, platinum, palladiurn, lead, tin, nickel, cobalt, cadmium, bismuth, ruthenium, thallium, indium, rhodium, osmium, iridium, copper, silver and gold tellurides and selenides which comprises precipitating the said composition by admixture of a solution containing the desired metal ions and the ions of a compound selected from the class consisting of tellurium and selenium by admixture with a solution of an unsaturated organic acid reducing agent selected from the group consisting of crotonic and malonic acids in the proportion of from 0.1 to 25.0 molecular Weights of the said organic acid reducing agent per atomic Weight of the said tellurium and selenium, the said precipitation being conducted in the presence of a compound selected from the group consisting of tartaric acid, citric acid and malic acid, the proportion of the said compound being from 0.1% to 20% by weight relative to the weight of the total solutions present and isolating the desired metal compound from the mixture.

M References Cited in the tile of this patent UNITED STATES PATENTS 2,534,562 Thomsen Dec. 19, 1950 2,860,954 Buelter et al. Nov. 18, 1958 FOREIGN PATENTS 142,728 Australia Aug. 6, 1951 OTHER REFERENCES,

Feigl: Chemistry of Specific, Selective and Sensitive Reactions," Academic Press 1110., publishers, New York, 1949, PP. 6-408.

Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry, Longmans, Green and Co., New York, vol. 10, 1930, pp. 771, 778 and 801; vol. 11, 1931, pp. 33, and 64.

Thorpe: Dictionary of Applied Chemistry, Long- Mans, Green and Co., New York, 1916, vol. V, p. 434. 

1. METHOD FOR THE PREPARATION OF A COMPOUND SELECTED FROM THE CLASS CONSISTING OF MERCURY, PLATINUM, PALLADIUM, LEAD, TIN, NICKEL, COBALT, CADMIUM, THALLIUM, INDIUM, BISMUTH, RUTHENIUM, RHODIUM, OSMIUM, IRIDIUM, COPPER, SILVER AND GOLD TELLURIDES AND SELENIDES WHICH COMPRISES PRECIPITATING THE DESIRED COMPOUNDS FROM MEDIA CONTAINING THE RESPECTIVE MEMBERS THEREOF BY ADMIXTURE WITH A PRECIPITATING AGENT CONSISTING OF A MEMBER OF THE CLASS OF CROTONIC AND MALONIC ACIDS IN THE PROPORTION OF FROM 0.1 TO 25.0 MOLECULAR WEIGHT PER ATOMIC WEIGHT OF TELLURIUM AND SELENIUM, AND ISOLATING THE DESIRED COMPOUND FROM THE MIXTURE. 